\Hold"fast`\, n.
1. Something used to secure and hold in place something else,
as a long fiat-headed nail, a catch a hook, a clinch, a
clamp, etc.; hence, a support. ``His holdfast was gone.''
--Bp. Montagu.
2. (Bot.) A conical or branching body, by which a seaweed is
attached to its support, and differing from a root in that
it is not specially absorbent of moisture.